Kidney stones have always been a painful affliction to men and women of all ages. These stones, also known as renal calculi, develop within the kidney and are in many cases too large to pass through the ureter and urethra. The stones are composed of rigid crystalline components such as calcium oxalates and phosphates and are often difficult to destroy. Thus, kidney stones must either be surgically removed or somehow reduced to fragments small enough to comfortably pass through the ureter and urethra.
Various techniques have been developed in an attempt to provide a safe and effective method of eliminating kidney stones from the human body. One such technique involves the dissolution of urinary calculi by organic or inorganic acid solutions or reagents. This technique suffers from the fact that the acid solutions or reagents can be very irritating to the patient undergoing treatment.
Presently, several non-invasive sonic methods and invasive ultrasonic and laser fragmentation methods to destroy kidney stones are being explored. For example, extracorporeal shock wave lithotripsy (ESWL) is of considerable current interest and involves applying focused intense acoustic impulses which produce pressure waves greater than one kbar in amplitude. These acoustic impulses are repeatedly applied to the stone until the stone is pulverized or comminuted into fragments small enough to be passed through the ureter and urethra. Unfortunately, the acoustic pulses cannot be precisely focused onto the stone and therefore portions of the healthy kidney normally receive some of the concentrated shock waves. Since the pulses often have to be repeated up to 2000 times, the healthy portions of the kidney receiving the shock waves can be injured, resulting in hematuria. Furthermore, the shock-producing electrodes utilized in ESWL are expensive and have a limited useful life. Since ESWL requires extensive repetition of acoustic impulses, the electrodes frequently become exhausted and require replacement which results in considerable lithotripter equipment expense and inconvenience.
A need therefore exists for a method of acoustically comminuting kidney stones which utilizes a reduced number of acoustic impulses so as to minimize trauma to healthy tissue and reduce exhaustion of shock-producing electrodes in ESWL equipment. The novel technique disclosed hereinafter should overcome these deficiencies associated with current renal calculi comminution techniques.